U.S. patent number 5,256,134 [Application Number 07/663,875] was granted by the patent office on 1993-10-26 for conformable bandage.
This patent grant is currently assigned to Smith & Nephew plc. Invention is credited to Philip Ingham.
United States Patent |
5,256,134 |
Ingham |
October 26, 1993 |
Conformable bandage
Abstract
A warp knitted fabric is described in which each individual wale
contains stitches formed from both elastic and inelastic yarn. The
fabric is extensible in the direction of the wales and may be used
as a substrate in an orthopaedic splinting bandage. Orthopaedic
splinting bandages are also described which comprise the warp
knitted fabric coated with a hardenable resin such as an isocyanate
terminated propolymer. The lengthwise extensibility of the
substrate makes the uncured bandage conformable during application
to the body.
Inventors: |
Ingham; Philip (Hebden Bridge,
GB) |
Assignee: |
Smith & Nephew plc
(GB)
|
Family
ID: |
26294372 |
Appl.
No.: |
07/663,875 |
Filed: |
March 6, 1991 |
PCT
Filed: |
September 11, 1989 |
PCT No.: |
PCT/GB89/01065 |
371
Date: |
March 06, 1991 |
102(e)
Date: |
March 06, 1991 |
PCT
Pub. No.: |
WO90/02539 |
PCT
Pub. Date: |
March 22, 1990 |
Foreign Application Priority Data
|
|
|
|
|
Sep 9, 1988 [GB] |
|
|
8821223 |
Jan 10, 1989 [GB] |
|
|
8900437 |
|
Current U.S.
Class: |
602/8; 442/164;
442/306; 602/5; 66/169R; 66/170; 66/195; 66/202 |
Current CPC
Class: |
A61F
13/04 (20130101); D04B 21/18 (20130101); A61F
2013/00136 (20130101); Y10T 442/463 (20150401); Y10T
442/413 (20150401); Y10T 442/2861 (20150401); D10B
2509/024 (20130101) |
Current International
Class: |
A61F
13/04 (20060101); D04B 21/14 (20060101); D04B
21/18 (20060101); A61F 13/00 (20060101); A61F
005/04 (); A61F 013/00 () |
Field of
Search: |
;428/259,260,230,254,288,289,290,231,245,253 ;602/5,8,44,45,76
;66/169R,190,195,202,170 ;128/90,89R,155,156 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1165201 |
|
Mar 1964 |
|
DE |
|
2082214A |
|
Aug 1980 |
|
GB |
|
Other References
Textile Institute, Textile Terms and Definitions, p. 101, etc.,
Eighth Edition, 1986..
|
Primary Examiner: Lesmes; George F.
Assistant Examiner: Withers; James D.
Attorney, Agent or Firm: Rosenman & Colin
Claims
I claim:
1. A conformable, hardenable, orthopaedic splinting bandage
comprising a warp knitted fabric substrate coated with a curable
resin wherein said fabric substrate contains individual wales, each
individual wale comprising a repeating pattern of loops knitted
from an elastic yarn and an inelastic yarn, said elastic yarn or
inelastic yarn mislapping when not knitted to form said loops.
2. A bandage as claimed in claim 1 wherein said curable resin is a
water curable resin.
3. A bandage as claimed in claim 2 wherein said water curable resin
is an isocyanate terminated prepolymer.
4. A bandage as claimed in claim 1 wherein in each wale of the
fabric substrate, the elastic or inelastic yarn which is not being
knitted as a loop is laid into the knitted stitches of a yarn which
is being knitted as a loop.
5. A bandage as claimed in claim 1 wherein in each wale of the
fabric substrate, the yarn which is not being knitted as a loop is
allowed to float on the surface of the fabric.
6. A bandage as claimed in claim 1 wherein the repeating pattern
along the wale is 2 inelastic yarn loops to 1 elastic yarn loop or
2 elastic yarn loops to 1 inelastic yarn loop.
7. A bandage as claimed in claim 1 wherein the coated bandage has
an extension of at least 25%.
8. A bandage as claimed in claim 1 wherein the substrate has a
weight per unit area of 100 to 350 gm.sup.-2 and the resin is 40 to
60% of the total weight of the bandage.
Description
The present invention relates to a knitted fabric which is suitable
for use as a substrate in hardenable orthopaedic splinting
bandages. The present invention also relates to an orthopaedic
bandage comprising a resin-coated fabric substrate which has
improved conformability.
Conventional orthopaedic splinting bandages for use in the
treatment of bone fractures or other conditions requiring
immobilization of part of the body are formed from a substrate
impregnated with a substance which hardens to a rigid structure
after wrapping the bandage around the body. Traditionally Plaster
of Paris has been used but more recently certain plastics have
gained acceptance as replacements for Plaster of Paris. Such new
bandages are lighter, waterproof and permeable to X-rays.
Substrates for use with these plastics have included glass fibre
fabrics such as those described in U.S. Pat. Nos. 4,502,479,
4,609,578, 4,668,563 and 4,323,061.
One disadvantage of substrates including glass fibres is that the
casts formed from them can become brittle and break down during
wear and hence need to be replaced before healing is complete. A
second disadvantage is that during cast removal irritating glass
dust or fibres may be generated. These disadvantages would be
mitigated by using a substrate which gave a durable cast and did
not give rise to irritating fibres on cast removal. However,
heretofore such substrates have lacked the conformability and cast
strength found when using glass fibre substrates.
A knitted fabric has now been made containing individual wales
knitted from elastic yarn and inelastic yarn and when using this
fabric as a substrate a bandage is achieved which has good
conformability compared to those employing existing fabric
substrates. Even more surprisingly the cast formed using this novel
substrate does not slow a loss of strength compared to a cast which
employs a glass fibre substrate. A further advantage of this fabric
is that it is found to possess surprisingly good dimensional
stability that is it has little or no propensity to curl which aids
processing such as coating.
Although the presence of wales which are knitted from both elastic
and inelastic yarns is most useful in substrates which do not
contain glass fibres it is envisaged that the same construction
could be used with glass fibres to advantage.
The present invention provides a warp knitted fabric which contains
wales which are knitted from both elastic and inelastic yarns.
The warp knitted fabric of the invention is an elastic fabric that
is to say that it possesses recoverably extensibility in a
direction parallel to the wales which contain the elastic yarn. An
elastic yarn is a yarn formed form an elastomer. An elastomer may
be defined as a rubber or polymer which has high extensibility
together with rapid and substantially complete elastic recovery.
Suitable elastic yarns for use in the invention include those which
have an elongation at break of greater than 100% and more suitably,
greater than 300%.
The warp knitted fabric of the invention is described herein with
reference to its use as a substrate in an orthopaedic bandage. It
is envisaged that the fabric may be used in other applications
where its elastic properties may be employed to advantage, for
example in bandages and clothing.
In one favoured aspect therefore the present invention provides a
warp knitted fabric suitable for use as a substrate in a resin
coated, water hardenable orthopaedic splinting bandage which fabric
contains wales which are knitted from both elastic and inelastic
yarns.
In a second aspect the present invention provides a conformable
hardenable orthopaedic sprinting bandage comprising a warp knitted
fabric substrate coated with a curable resin which fabric substrate
contains wales knitted from both elastic and inelastic yarns. Most
suitably the resin is a water curable resin so that the bandage is
one which hardens after being exposed to water.
It is clear from the above that each individual wale is knitted
from both elastic and inelastic yarns. The fabric normally has a
planar surface.
The orthopaedic splinting bandages of the present invention possess
lengthwise extensibility by virtue of the presence of elastic yarns
knitted into the wales of the fabric. Suitable elastic yarns
include those formed from natural rubber or a synthetic elastomer
such as polyisoprene, polybutadiene, copolymers thereof,
elastomeric ethylene-propylene copolymers and thermoplastic
elastomers including block copolymers of styrene and butadiene or
isoprene or an elastic polyurethane yarn. A particularly preferred
elastic yarn is a spandex yarn, that is a polyurethane yarn for
example Lycra yarn (Trade mark).
The inelastic yarns of the knitted substrate may be formed from
yarns which include yarns formed from polypropylene, polyester,
polyamide, polyethylene, cotton viscose. A preferred yarn is
polyester yarn, including multifilament or monofilament
polyethylene terephthalate yarn.
A wale when used herein- means a column of loops along the length
of the fabric. In the fabric of the invention some of the loops in
each wale are formed from either elastic yarn and some formed from
inelastic yarn and are preferably knitted in a repeating pattern
along the wale. When not being knitted as a loop the yarn mislaps
until required for knitting again. The non-knitted yarn may be laid
into the knitted stitches or may be allowed to float on the surface
of the fabric. Typically in a 4 bar warp knitted fabric there may
be 2 polyester stitches to 1 elastomer stitch or vice versa. This
is unlike previously known elastic fabrics where either all the
loops of the wales are formed from elastic yarn or elastic yarn is
incorporated as an inlay along a wale formed from inelastic yarn.
This new manner of knitting surprisingly gives the additional
advantage of dimensional stability, shown by lack of inward curl,
over a wider range of mesh dimensions.
Suitably the lengthwise extension of the substrate that is in the
direction of the wales, may be from 15 to 200%, more suitably 25 to
160% and preferably 50 to 150%. The degree of extension may be
varied according to the type of elastic yarn chosen but the above
ranges are suitable for substrates used in orthopaedic
bandages.
When coated with resin the lengthwise extension can be at least
25%, more suitably at least 40% and preferably at least 50%. The
upper limit to lengthwise extensibility can be 60%, more suitably
70% and preferably at least 80%.
Suitably the widthwise extension of the substrate may be from 20 to
150%, more suitably 20 to 100%, most suitably 25 to 60% and
preferably 30 to 50% for example 45%.
The elastic yarns in the substrate appear to cause the substrate to
return to its original length after stretching and so facilitate
conformability of the substrate to the patient's body. The bandages
were observed to conform easily to various shaped formers made to
represent parts of the body.
Suitably the knitted substrate has a low power, that is the force
required to stretch the substrate for a given percentage extension.
If this power is low then this will help to prevent constriction of
the patient's limb after the bandage has been applied.
The lengthwise extension may be measured using an Instron Tensile
Testing Machine. A 10 cm length of substrate may be clamped in the
jaws of the machine and the jaws separated at constant speed. A
conventional stress-strain curve for the substrate may be recorded.
The extension at a given load and the load required to give a given
extension can be calculated from the curve for the substrate under
test.
For the best shelf life of the resin coated substrates, the elastic
yarn used in the substrate must be compatible with the resin with
which it is coated. Suitable compatible elastic yarns may be
identified by forming a bandage incorporating the elastic yarns and
coating with the resin and ageing in a sealed container for 12
weeks at 55.degree. C. If at the end of this time the bandage may
be used to form a satisfactory cast then the elastic yarn is
suitable particularly for use in conjunction with the resin. The
unsuitability of some elastic yarns may be overcome by means of
coating or wrapping the yarn with other inert materials such as
cotton or nylon yarn. For example elastic polyurethane yarns may be
wrapped in cotton or nylon.
Suitably the substrate may have a thickness of from 0.375 mm to 4.0
mm, more suitably will be 0.50 mm to 3.00 mm thick and preferably
1.00 mm to 2.00 mm thick, for example 1.50 mm.
Suitably the knitted substrate may have a weight per unit area when
relaxed of from 50 to 500 gm.sup.-2 more suitably may have a weight
of from 100 to 350 gm.sup.-2, and preferably a weight of between
150 and 220 gm.sup.-2 for example 170 g, 175, 180, 185 and 190
gm.sup.-2.
Suitably the fabric may be produced on a warp knitting machine or
on a crochet knitting machine. The fabric is a warp knitted fabric
comprising chain or pillar stitches linked by under-lapped inlay
threads. In the fabric of the invention the elastic yarn is
incorporated in the pillar stitch so as to give the lengthwise
stretch.
Normally when producing a pillar or chain stitch in a warp knitted
fabric the same yarn guide always overlaps the same needle. This
produces chains of loops in unconnected wales which are then
connected together by underlaps of yarn from second or other guide
bars to form the fabric. When the elastic yarn is present at least
two yarn guides are used to produce each pillar stitch. The first
guide feeds the in-elastic yarn to the needle which knits one or
more courses before being withdrawn to let in the second guide
which feeds in the elastic yarn to the needle which again knits for
one or more courses before the second guide withdraws and the first
guide is let in. This cycle is repeated as knitting proceeds. The
knitting provides a stable fabric with a reduced tendency to
curl.
The resins used in the orthopaedic bandage of the invention may be
any curable resin which will satisfy the functional requirements of
an orthopaedic cast. The preferred resins are those cured with
water or moisture and include the resins described in U.S. Pat.
Nos. 4,667,661, 4,502,479, 4,574,793, 4,433,680, 4,427,002,
4,411,262, 3,932,526, 3,908,644, 3,630,194, in German
Offenlengungsschrift No. 2651089 and in European Patent
Applications Nos. 35517, 57988, 86621 and 94222.
Aptly the resin used to coat the fabric substrate may be a water
curable isocyanate terminated prepolymer system. Among suitable
prepolymer systems are those identified in U.S. Pat. Nos.
4,411,262, 4,427,002, 4,433,680 and 4,574,793. Particularly
preferred are those systems disclosed and claimed in U.S. Pat. Nos.
4,427,002 and 4,574,793 the disclosures of which are incorporated
herein by cross-reference.
Suitably the bandage may be formed by coating or impregnating the
substrate with the resin in the manner described in those patents,
particularly in U.S. Pat. No. 4,427,002.
Suitably the weight of resin on the substrate is from 150 to 650
gm.sup.-2 and mare suitably from 150 to 500 gm.sup.-2, most
suitably a weight of 200 to 450 gm.sup.-2 and preferably 225 to 450
gm.sup.-2 most preferably between 250 to 400 gm.sup.-2. The weight
of resin may be chosen so that suitably 40 to 60% of the total
weight of the bandage is resin and more suitably 55 to 60% of the
total weight. Thus if the fabric weight is 180 gsm and the resin
coating is 55-60% of the bandage then the weight of resin taken is
220-270 g.
The formed bandages may be packaged by heat sealing in waterproof
pouches such as those formed from metal foil polyethylene laminates
or polyethylene pouches.
In use the bandages may be brought into contact with water and
wrapped around the injured part of the body. The setting bandage
has a working time which is sufficient to allow the bandage to be
positioned on the limb and a set time which is the tine taken for
the cast to become rigid. Apt working times are 1 to 6 minutes and
apt set times are 5 to 30 minutes.
The cast incorporating the substrate of the invention is readily
removable by conventional means such as by cutting with a
conventional circular saw. Large casts may be removed using a
single cut along the length of the cast which is not always
achievable with fibre glass substrate casts.
The build-up of strength in the cast was assessed by wrapping the
resin-coated substrate round a former to make a cylinder. The
former is removed and the cylinder wall clamped in a Instron
Tensile Testing machine so as to measure diametral compression and
extension forces. The machine is adapted so that the moving clamp
would oscillate between positions 2.5 mm from the rest position.
The force required to deform the cast as it set over a period of
time is measured. The results were recorded an a chart recorder. A
bandage formed according to Example 2, which was 4 layers thick,
was tested in comparison with a conventional glass fibre based
bandage using cylinders formed of 5 layers of bandage. The bandage
according to the invention was greater in strength to the glass
fibre bandage both on initial setting and after 24 hours.
______________________________________ Rigidiy (kg/cm width) Time
after initiation of set 15 mins 30 mins 24 hr
______________________________________ Bandage of Example 2 2.7 3.4
5.3 (4 layers) Glass fibre-based 2.1 2.65 4.5 bandage (5 layers
______________________________________
For the following examples the knitting machine has 12 needles per
inch and is threaded half sett. The knitting notation is an English
notation.
EXAMPLE 1
Preparation of substrate
A substrate was prepared by knitting together elastic polyurethane
yarns and polyester yarns. The elastic polyurethane yarns were
formed from a segmented polyurethane and are available as Lycra
spandex yarns. The yarns had a weight per unit length of 156 dtex.
The yarns may be wrapped in nylon or cotton or other yarns. The
polyester was a multifilament polyethylene terephthalate with a
weight per unit length of 1100 dtex.
The knitting pattern was as follows:
______________________________________ Bar 1 1-0/0-1/1-1 (Polyester
yarn) Bar 2 0-0/1-1/1-0 (Lycra yarn) Bar 3 3-3/2-2/3-3/0-0/1-1/0-0
(Polyester yarn) Bar 4 0-0/1-1/0-0/3-3/2-2/3-3 (Polyester yarn)
______________________________________
The machine was 12 gauge and each guide bar was threaded half
sett.
The fabric so knitted has 30 to 34 wales/10 cm width and 35 to 43
courses/10 cm. The fabric was knitted at a 10 cm width. The fabric
has a weight per unit area of 200 gm.sup.-2.
The knitted fabric has an extension in the width direction of 80%
and extension in the lengthewise direction of 50% (approx.).
This fabric is suitable for use as a substrate in an orthopaedic
splinting bandage.
EXAMPLE 2
Preparation of Bandages
A water curable polyurethane resin system comprising a polyurethane
prepolymer described in U.S. Pat. No. 4,574,793 as prepolymer A and
containing methane sulphonic acid as stabiliser and bis (2,6
dimethyl morphilino) diethyl ether as catalyst is coated onto a
knitted fabric described in Example 1 using the process described
in U.S. Pat. No. 4,427,002. The weight of the resin applied is 240
gm.sup.-2 which means that the resin forms 55% of the weight of the
bandage. The coated bandage had a lengthwise extension of 25%
approximately.
The bandage strip is cut into 3 meter lengths and spooled onto
rolls. The bandage rolls are then placed into pouches which are
heat sealed to prevent exposure of the contents to moisture.
A bandage is made into a cast by dipping the bandage roll in water
and wrapping around a body member.
EXAMPLE 3
Preparation of Substrate
A fabric was prepared by knitting together elastic polyurethane
yarns and polyester yarns. The elastic polyurethane yarns are
formed from a segmented polyurethane and are available a-s Lycra
spandex yarns and may be wrapped in nylon or cotton. The yarns had
a weight per unit length of 156 dtex. The polyester was a
multifilament polyethylene terephthalate with a weight per unit
length of 1100 dtex.
The knitting pattern was as follows:
______________________________________ Bar 1
1-1/1-1/1-0/0-0/0-0/0-1 (Lycra fibre) Bar 2 1-0/0-1/1-1/1-0/0-1/1-1
(Polyester fibre) Bar 3 3-3/2-2/3-3/0-0/1-1/0-0 (Polyester fibre)
Bar 4 0-0/1-1/0-0/3-3/2-2/3-3 (Polyester fibre)
______________________________________
The machine was 12 gauge and each guide bar was threaded half
sett.
The fabric knitted according to this pattern has a weight per unit
area of 175 gm.sup.-2, 30 to 34 wales/10 cm width and 35 to 43
courses/10 cm length.
This fabric is suitable for use in an orthopaedic splinting
bandage.
EXAMPLE 4
Preparation of Bandages
A bandage was prepared using the fabric described in Example 3 as
the substrate in the manner described in Example 2.
EXAMPLE 5
Preparation of Fabric
A fabric was prepared by knitting together an elastic polyurethane
yarn and polyester yarns. The elastic polyurethane yarn was formed
from a segmented polyurethane available as a Lycra spandex yarn.
The yarn had a weight per unit length of 156 dtex. The fibres may
be wrapped in nylon or cotton or other suitable yarns. The
polyester was a multifilament polyethylene terephthalate with a
weight per unit length of 1100 dtex.
The knitting pattern was as follows:
______________________________________ Bar 1 Polyester 1-0/0-1/1-1
Bar 2 Lycra 0-0/1-1/1-0 Bar 3 Polyester 3-3/2-2/3-3/0-0/1-1/0-0 Bar
4 Polyester 0-0/1-1/0-0/3-/2-2/3-3
______________________________________
The machine was 12 gauge and each guide bar was threaded half
sett.
The knitting machine was set to knit 4.0 courses/cm. In the wales,
the knitting was such that the Lycra stitch was the first stitch
after the inlay crossover. The repeat pattern in the pillar stitch
was 2 polyester:1 Lycra stitch.
The knitted fabric has an extension in the width direction of
75-80% and the extension in the lengthwise direction is 50%
(approx).
The fabric is suitable for use as a substrate in an orthopaedic
splinting bandage.
EXAMPLE 6
Preparation of Fabric
A fabric was prepared in a similar manner to and from the same
yarns as described in Example 5 except that Bar 1 carried the
elastic yarn and Bar 2 carried a polyester yarn. In this
construction the pillar stitch repeat is now 2 Lycra stitches:1
polyester stitch. The polyester stitch is positioned on the inlay
cross-over. When not knitting the guide bar 2 in-lap the polyester
yarn inside the Lycra stitches.
The fabric has similar characteristics to that prepared as in
Example 5.
EXAMPLE 7
Preparation of Fabric
A fabric was prepared from similar materials as those described in
Example 5.
The knitting pattern was as follows:
______________________________________ Bar 1 Polyester 0-0/1-1/1-0
Bar 2 Lycra 1-0/0-1/1-1 Bar 3 Polyester 3-3/2-2/3-3/0-0/1-1/0-0 Bar
4 Polyester 0-0/1-1/0-0/3-3/2-2/3-3
______________________________________
The machine was 12 gauge and each guide bar was threaded half
sett.
In this construction the pillar stitch repeat is two Lycra
stitches:1 polyester stitch. The polyester stitch is positioned on
the inlay cross-over point. When not knitting the guide bar 2
allows the polyester yarn to float on the surface of the fabric
rather than to inlay up the pillar stitch inside the Lycra
stitches.
The fabric has similar characteristics to that prepared in Example
5.
EXAMPLE 8 TO 11
Preparation of Fabric
Suitable fabrics are prepared by using polypropylene yarn with the
same knitting patterns described in Examples 1, 5, 6 and 7. The
polypropylene yarn used is a 70 filament yarn of weight per unit
length of 470 dtex.
EXAMPLE 12
Preparation of Bandages
A resin was formed from Isonate 143L (47.8%), Isonate 240 (14.7%),
Voranol (3.5%), propylene glycol (31.9%), antifoam (0.3%), methane
sulphonic acid (0.03%) and bis (2.6-dimethyl morpholino-N-ethyl)
ether (1.8%).
The resin was spread at 54% by weight of the weight of the total
bandage onto the substrate described in Example 1 (10 cm.times.10
cm) using a hopper and doctor knives in a conventional manner under
nitrogen. The bandage was wound onto a core to form a roll and
sealed into an aluminium foil pouch under argon.
A bandage was removed from a pouch and immersed in water. The
bandage was squeezed three times under water to ensure wetting,
removed, shaken and applied to a mandrel. The bandage provided a
suitable cast.
EXAMPLE 13 TO 20
Preparation of Bandages
A resin as described in Example 12 was applied to fabrics described
in Examples 3, 5 to 11 by the process described in Example 12. The
coated substrates provided suitable bandages for forming casts.
* * * * *